Solid ink or phase change ink printers conventionally use ink in a solid form, either as pellets or as ink sticks of colored cyan, yellow, magenta and black ink fed into shape coded openings. These openings fed generally vertically into the heater assembly of the printer where they were melted into a liquid state for jetting onto the receiving medium. The pellets were fed generally vertically downwardly, using gravity feed, into the ink loader. These pellets were elongated with separate multisided shapes each corresponding to a particular color.
Solid ink sticks have been typically either gravity fed or spring loaded into a feed channel and pressed against a heater plate to melt the solid ink into its liquid form. These ink sticks were shape coded and of a generally small size. One system used an ink stick loading system that initially fed the ink sticks into a preload chamber and then loaded the sticks into a load chamber by the action of a transfer lever. Earlier solid or hot melt ink systems used either a flexible web of hot melt ink that was incrementally unwound and advanced to a heater location or particulate hot melt ink that was delivered by vibrating the particulate into the melt chamber.
In previously known phase change ink jet printing systems, the interface between a control system for a phase change ink jet printer and a solid ink stick provided little information about the solid ink sticks loaded in the printer. For instance, previously known control systems are unable to determine accurately the amount of ink ejected from the printhead of the printer. Once ink has been melted and reaches the print head of a printer, the liquid ink flows through manifolds to be ejected from microscopic orifices by piezoelectric transducers (PZT). An electric pulse is applied to the PZTs to cause droplets of ink to be ejected from the orifices. The duration and amplitude of the electrical pulse applied to the PZTs is controlled so that a consistent volume of ink may be ejected by each orifice. Thus, the total amount of ink that has been “theoretically” used may be calculated by counting the number of times ink has been ejected from the PZTs and multiplying that number by the amount of ink that should have been ejected during each pulse. The amount of ink ejected from the PZTs may vary or drift over time due to a number of factors, such as, for example, prolonged use. Previously known control systems are generally not able to determine accurately the amount of drift occurring in the volume of ink ejected from the printhead.
As another example, previously known control systems are typically only able to sense when the first color (of the four colors) of solid ink in an ink loader reaches a “low” volume state or an “out of ink” state. Additionally, these control systems are generally not able to determine which of the colors caused the “low” or “out of ink” state or the fill status of the other colors of solid ink that have not caused the “low” or “out of ink” state.
Moreover, previously known control systems are limited in their ability to gain specific information about an ink stick that is currently loaded in the feed channels. For instance, control systems are not able to determine if the correct color of ink stick is loaded in a particular feed channel or if the ink that is loaded is compatible with that particular printer. Provisions have been made to ensure that an ink stick is correctly loaded into the intended feed channel and to ensure that the ink stick is compatible with that printer. These provisions, however, are generally directed toward excluding wrong colored or incompatible ink sticks from being inserted into the feed channels of the printer. For example, the correct loading of ink sticks has been accomplished by incorporating keying, alignment and orientation features into the exterior surface of an ink stick. These features are protuberances or indentations that are located in different positions on an ink stick. Corresponding keys or guide elements on the perimeters of the openings through which the ink sticks are inserted or fed exclude ink sticks which do not have the appropriate perimeter key elements while ensuring that the ink stick is properly aligned and oriented in the feed channel.
While this method is effective in ensuring correct loading of ink sticks in most situations, there are still situations when an ink stick may be incorrectly loaded into a feed channel of a printer. For example, world markets with various pricing and color table preferences have created a situation where multiple ink types may exist in the market simultaneously with nearly identical size/shape ink and/or ink packaging. Thus, ink sticks may appear to be substantially the same but, in fact, may be intended for different phase change printing systems due to factors such as, for example, market pricing or color table. In addition, due to the soft, waxy nature of an ink stick body, an ink stick may be “forced” through an opening into a feed channel. The printer control system, having no information regarding the configuration of the ink stick, may then conduct normal printing operations with an incorrectly loaded ink stick. If the loaded ink stick is the wrong color for a particular feed channel or if the ink stick is incompatible with the phase change ink jet printer in which it is being used, considerable errors and malfunctions may occur.